Biodegradable bioadhesive controlled release system of nano-particles for oral care products

ABSTRACT

The present invention relates to a controlled release system useful for site specific delivery of biologically active ingredients or sensory markers, over an extended period of time, targeting biological surfaces comprising the oral cavity and mucous membranes of various tissues, as well as the controlled release of the biological active ingredients or sensory markers. The controlled release system of the present invention is a nano-particle, having an average particle diameter of from about 0.01 microns to about 10 microns, which comprises a biodegradable solid hydrophobic core and a bioadhesive/mucoadhesive positively charged surface. The invention also relates to the use of the nano-particles of the present invention in consumer oral hygiene products, such as toothpaste or mouthwash, for treatment and prevention of periodontal disease. The nano-particles of the present invention are particularly effective for targeted controlled delivery of biological active ingredients into the periodontal pocket. The present invention also provides synchronizing the release of the biologically active ingredient with that of the sensory markers to convey to the consumer the product performance and signal that a new application of the product is needed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to bioadhesive controlled release systems usefulfor targeted delivery of biologically active ingredients, such asanti-septic or antibacterial materials, anti-inflammatory, and otheractive ingredients that interdict the attachment, propagation, growthand or colonization of bacteria on teeth or sensory markers such asflavors and cooling agents to biological surfaces comprising the oralcavity and mucous membranes of various tissues, as well as the releaseof these active ingredients or sensory markers over an extended periodof time. More specifically, the invention pertains to biodegradablebioadhesive and mucoadhesive nano-particles for oral hygiene productssuch as toothpaste or mouthwash, that sustain the release of biologicalactive ingredients for treatment and prevention of periodontal diseaseor the release of sensory markers that provide extended sensation offreshness and malodor coverage over an extended period of time.

2. Description of the Related Art

Decreasing the amount of bacteria in the mouth has long been the targetof personnel working in the health care field. The oral care industryand health research communities have searched for many years for a wayto interdict the attachment, propagation, growth and or colonization ofbacteria on teeth since adherence of bacteria is the start of apernicious chain of events leading to the formation of homecare-resistant plaque, calculus, and ultimately, tooth-loss. As the lifeexpectancy of people in developing countries has increased, dental careplays a larger role in overall health, and developing countries arebecoming more aware of the importance of oral hygiene. Considering theprevalence of periodontal disease, there is an ongoing need forimproved, more effective agents, as well as technology, that inhibitplaque growth to maximize the reduction of oral decay and diseaseassociated with plaque formation.

Periodontal disease, also known as pyorrhea or gum disease, is a majorcause of tooth loss in adults. Tooth loss from periodontal disease is asignificant problem beginning at about age 35, or even younger. It isestimated that about 4 out of 5 persons already have gingivitis and 4out of 10 have periodontitis. 75% of the US population suffers fromperiodontal disease and this epidemic costs billions of dollars a year.The greatest single cause of periodontal disease is poor hygiene,indicated by the appearance of bacterial plaque and tartar (calcifiedplaque). It is believed that plaque and tartar are more sinister whenthey occur below the gum line than when they occur at or above the gumline.

Several approaches to fight periodontal disease have been described inpatents and in literature. One of the approaches uses liposomes todeliver biologically active ingredients to the oral cavity. Severalreports of liposome suspensions containing bioadhesive polymers havebeen published. The problems with using liposomes and structuredvesicles as delivery devices are that these types of systems areunstable and can only be used for encapsulation of certain types ofmaterials. Stability has become the major problem limiting the use ofliposomes for controlled delivery, both in terms of shelf life and afteradministration. Liposomes and vesicles do not remain intact or availablein vivo for more than a few hours to a couple of days.

U.S. Pat. No. 5,989,535 discloses a polymeric controlled releasecomposition specifically targeted to the organs that contain mucusmembranes at the interface. The invention discloses a polymericbioadhesive composition that delivers drugs to the target tissue in asustained manner. The bioadhesive polymer is a water dispersible highmolecular weight crosslinked polyacrylic acid copolymer with freecarboxylic acid groups further crosslinked with a combination mono, diand polyvalent metal ions, cationic polymers and surfactants. The typeof metal ion and the concentration can be adjusted to get the desiredadhesive properties along with several physical properties that areimportant to the formulation of dosage forms.

U.S. Pat. No. 5,993,846 discloses methods for making oil-in-wateremulsions having mucoadhesive properties. The emulsion includes ahydrophobic core, a surfactant, and a mucoadhesive polymer which is apolymer or copolymer of acrylic acid or methacrylic acid, a poly(methylvinyl ether/maleic anhydride)copolymer, pectin, alginic acid, hyaluronicacid, chitosan, gum tragacanth, karaya gum or carboxymethylcellulosesurrounding the hydrophobic core. Emulsions of this invention contain abioadhesive macromolecule or polymer in an amount sufficient to conferbioadhesive properties. The bioadhesive macromolecule enhances thedelivery of biologically active agents on or through the target surface.The bioadhesive macromolecule may be selected from acidic nonnaturallyoccurring polymers, preferably having at least one acidic group per fourrepeating or monomeric subunit moieties, such as poly(acrylic)- and/orpoly(methacrylic)acid (e.g., Carbopol, Carbomer), poly(methylvinylether/maleic anhydride)copolymer, and their mixtures and copolymers;acidic synthetically modified natural polymers, such ascarboxymethylcellulose (CMC); neutral synthetically modified naturalpolymers, such as (hydroxypropyl)methylcellulose; basic amine-bearingpolymers such as chitosan; acidic polymers obtainable from naturalsources, such as alginic acid, hyaluronic acid, pectin, gum tragacanth,and karaya gum; and neutral nonnaturally occurring polymers, such aspolyvinylalcohol; or their mixtures. The ionizable polymers may bepresent as free acids, bases, or salts, usually in a final concentrationof 0.01-0.5% (w/vol).

U.S. Pat. No. 5,077,051 discloses bioadhesive microcapsules which permitthe sustained release of active agents such as therapeutic or cosmeticagents into, the oral cavity. The bioadhesive microcapsules capable ofsustained release comprise of xanthan gum, locust bean gum, a bulkingagent and an active agent. The microcapsules are spray-dried or coatedwith wax and are prepared by a process which comprises spray drying asolution comprising the active agent xanthan gum, locust bean gum and abulking agent.

U.S. Pat. No. 5,403,578 discloses a stable tooth and gum dentifrice thatincludes a non-aqueous carrier containing urea, hydrated silica,fluoride, sodium bicarbonate, pyrophosphate, and a peroxide, one or moreof the ingredients being microencapsulated and which in use functions asan aid in preventing periodontal disease by reducing incidents of plaqueas well as controlling tartar formation, and also as an aid inpreventing dental caries and oral odors; and the method of compoundingsuch improved tooth and gum paste. The microencapsulated peroxide mayconsist of a blend of 75% by weight of calcium peroxide and 25% byweight of calcium hydroxide. The peroxide constituent is provided withan ethylcellulose coating that consists of 6.5% by weight of thefinished product.

U.S. Pat. No. 6,007,795 discloses a method for inhibiting bacteria inthe mouth of a patient which includes placing a particle containing adegradable material and an anti-microbial agent in the mouth of thepatient. In general, the invention features a method for inhibitingbacteria in the mouth of a patient that includes placing a particlecontaining a degradable material and an anti-microbial agent into themouth of a patient. The saliva in the mouth causes the degradablematerial in the particle to degrade, resulting in the release of theanti-microbial agent in a controlled manner over time. The exterior ofthe particle is water-stable allowing the particles to be incorporatedinto, for example, aqueous rinses or pastes without the water in therinse or paste causing the degradable material to degrade prematurely,prior to use.

WO 93/00076 discloses a drug delivery system of microparticles having aspherical core composed of a biopolymer, preferably a protein such asalbumin or gelatin, which typically has been crosslinked or denatured tomaintain its structural coherency. The spherical core is suggested to becombined with a bioadhesive polymer.

U.S. Pat. No. 5,061,106, discloses capsules or microspheres in the tuftholes in which the bristles of a toothbrush are mounted. The capsules ormicrospheres include a disinfectant or medicant that is released duringuse. A dye may also be included in the structures. The dye also isreleased over time to enable the user to become aware of when thecontents of the capsules are depleted.

U.S. Pat. No. 5,939,080 discloses oral compositions and methods forreducing plaque in a human or lower animal subject comprising applyingto the teeth of the subject an oral composition comprising one or morehydrophobic solvents having one or more characteristics selected fromthe group consisting of a hydrogen bonding parameter of less than about7.0 and a water solubility of less than about 10%; one or morenon-polymeric surfactants wherein the weight ratio of hydrophobicsolvent to non-polymeric surfactant is from about 30:1 to about 1:2; andone or more aqueous carriers; wherein the oral composition is in theform of a toothpaste or mouthrinse, is non-ingestible, and has a pH offrom about 5.0 to about 9.5. Preferred hydrophobic solvents includetriacetin, diethyl malate, diethyl succinate, benzyl alcohol,phenylethyl alcohol, ethyl acetate, diethyl sebacate, ethylacetoacetate, diethyl tartrate, butyl lactate, and ethyl lactate. Themost preferred hydrophobic solvents are triacetin, diethyl malate,dietihyl succinate, benzyl alcohol, phenylethyl alcohol, and butyllactate. Suitable non-polymeric surfactants are those which arereasonably stable and foam throughout a wide pH range. The non-polymericsurfactants may be anionic, select nonionic, amphoteric, zwitterionic,cationic, or mixtures thereof.

U.S. Pat. No. 5,976,506 discloses oral care products such as toothpasteswith an improved sensorially-perceivable cleaning benefit. This isachieved by the inclusion in the oral care products of agglomerates,substantially free from organic and/or inorganic binding agents, wherebythe agglomerates are made of at least two, chemically and/or physicallydifferent particulate materials of specified particle sizes. Theinclusion of materials having a therapeutic benefit on the teeth or gumsin the agglomerates such as zinc citrate provides for a further benefitin that this material is slowly released from the agglomerates, thusproviding for a delivery of this material over a longer period. Uponuse, the gritty-feeling agglomerates will break-down into smallerparticles, thus giving the consumer the feeling of initial cleaning andsubsequent polishing.

U.S. Pat. No. 5,955,502 describes the use of fatty acid esters asbioadhesive substances. The fatty acid esters of the invention havemolecular weights below about 1000 dalton and the fatty acid componentof the fatty acid ester is a saturated or unsaturated fatty acid havinga total number of carbon atoms of from C₈ to C₂₂. Bioadhesive propertieswhere observed for fatty acid esters of glyceryl monooleate, glycerylmonolinoleate or glyceryl monolinolenate. A method is described foradministering active or protective substance to undamaged or damagedskin or mucosa of an animal such as a human by combining the active orprotective substance with a bioadhesive fatty acid ester. The createdparticles have no charge on their surface.

U.S. Pat. No. 4,780,320 discloses a controlled release drug deliverysystem for placement in the periodontal pocket. The microparticles areprepared by the solvent evaporation process and are between 10 and 500microns in size. The matrix of the microparticles consist of celluloseacetate, ethylcellulose, polystyrene, polysulfone, polycarbonate andlacticglycolic acid copolymers.

U.S. Pat. No. 6,042,792 disclose controlled, time-releasemicroparticulate active and bioactive compositions, including perfumingcompositions, for targeted delivery to skin, hair and fabric. Suchcompositions include the active or bioactive material in single phase,solid solution in a wax or polymer matrix also having coated thereon orcontaining a compatible surfactant. Also described are processes andapparatus for preparing such compositions and processes for using thesame.

In conventional controlled release systems no precautions are made inorder to localize the delivery system after administration and,furthermore, the contact time in vivo between the controlled releasesystem and a particular site is often so short that no advantages are tobe expected with respect to, e.g., modifying tissue permeability.

It is desirable to provide a biodegradable bioadhesive/mucoadhesivenano-particle controlled release systems that provide targeted deliveryand extended release of biological active ingredients and/or sensorymarkers for oral and hygiene product, wherein the release rate of thebiological active ingredient is synchronized with that of a sensorymarker.

SUMMARY OF THE INVENTION

The present invention relates to a controlled release delivery systemcomprising biodegradable bioadhesive nano-particles to providesite-specific delivery of biologically active ingredients or sensorymarkers for targeting and adhering to biological surfaces comprising theoral cavity and mucous membranes of various tissues. The nano-particleof the present invention sustains the release of the biological activeingredients or sensory markers over an extended period of time. Thepresent invention also provides a method for making biodegradablenano-particles having bioadhesive properties.

The nano-particles of the present invention comprise a cationicsurfactant that is entrapped and fixed to the particle surface. Thebioadhesive properties of the nano-particles are attributed to thepositively charged surfactant entrapped on the particle surface as thehydrophobic ends of the surfactants are embedded in the solid core andthe hydrophilic ends are exposed on the surface of the nano-particles.The cationic surface active materials useful in the present invention,are believed to attach to tooth surfaces via a complexing interactionbetween the cationic portion of the material and the proteinaceousportion of the tooth and thus predispose or condition the surface of thetooth so that the nano-particles will then adhere to the surface.

Preferably, the nano-particles are formed of a solid inner core. Thecombination of a solid inner core with a cationic exterior providesseveral advantages of the nano-particles as compared with conventionalmicrospheres, lipospheres, and microparticles, including highdispersibility in an aqueous medium, and a release rate for theentrapped substance that is controlled by the hydrophobic materialbarrier properties as well as the barrier properties of the hydrophiliclayer of cationic surfactant. There are also many advantages over otherdispersion-based delivery systems. Nano-particles have increasedstability as compared to emulsion-based delivery systems, includingvesicles and liposomes, and are more effectively dispersed than mostsuspension based systems. The substance to be delivered does not have tobe soluble in the vehicle since it can be dispersed in the solid matrix.The nano-particles of the present invention also have a lower risk ofreaction of substance to be delivered with the vehicle than in emulsionsystems because the vehicle is a solid inert material. The altering ofeither, or both, the inner solid core or the outer surfactant layer canmanipulate the release rate of the substance from the nano-particles.

The bioadhesive nano-particle compositions of the present invention cangenerally be incorporated into any suitable oral hygiene product knownin the art. Exemplary oral hygiene products include gels, chewing gums,toothpaste, and mouthwash. The oral hygiene product can be appropriatelyselected depending upon the physical location that the nano-particlesare to be delivered to, as well as the intended use of thenano-particles. The above-described exemplary oral hygiene products arepreferred in accordance with the present invention, since they permiteffective delivery of the bioadhesive nano-particles into the oralcavity. The toothpaste or mouthwash, containing the biodegradablebioadhesive nano-particles is useful for treatment and prevention ofperiodontal disease and extended sensation of freshness and malodorcoverage in the mouth over an extended period of time. Another aspect ofthe present invention is to provide oral hygiene products, such astoothpaste or mouthwash, containing the biodegradable bioadhesivenano-particles where the release rate of the biological activeingredients is synchronized with that of a sensory marker to convey tothe consumer the product performance.

In another aspect of the present invention the oral hygiene productscontaining the nano-particles of the invention are useful for targeteddelivery of biological active ingredients into the periodontal pocket.The controlled release system of the present invention takes advantageof the anatomical features of the gingiva and adjacent tissues, as asite that can hold the nano-particles for a prolonged period of time. Ithas also been found that the junctional epithelium, which joins thetooth surface and the keratinised gingival oral epithelium, is a thin,non-keratinised tissue, lacking membrane-coating granules which makethis region highly permeable to the nano-particles of the presentinvention.

Accordingly, the invention provides a biodegradable bioadhesivenano-particle for oral hygiene compositions of matter characterized byone or more of the following:

(i) site-specific delivery of biologically active ingredients or sensorymarkers, targeting and adhering to biological surfaces comprising theoral cavity and mucous membranes of various tissues;

(ii) controlled, continuous release of effective levels of biologicalactive ingredients or sensory markers over an extended period of time;

(iii) extended sensation of freshness or malodor coverage in the mouthover an extended period of time; and

(iv) the release rate of the biological active ingredients issynchronized with that of a sensory marker.

The invention also provides a method for producing the bioadhesivenano-particles, which comprises the steps of:

heating a hydrophobic core material to a temperature above the materialmelting point;

dissolving or dispersing the active ingredients or the sensory markerinto the melt;

dissolving or dispersing a positively charged surfactant, the biologicalactive agents and the sensory marker in the aqueous phase;

heating the composition to a temperature above the melting point of theformed mixture composed of the hydrophobic materials, active ingredientsor the sensory markers;

mixing the hot melt with the aqueous solution to form a suspension;

high shear homogenization of the suspension at a temperature above themelting temperature until a homogeneous fine suspension is obtained; and

rapidly cooling the suspension to below the melting point of the corematerial mixture composed of the hydrophobic materials, activeingredients, or sensory markers to form a dispersion.

The introduction of active agents such as anti-septic or antibacterialmaterials, anti-inflammatory, and other such active agents targetingbiological surfaces, comprising the oral cavity and mucous membranes ofvarious tissues, into the oral cavity by sustained release has theadvantage of reducing the number of times an active agent must beadministered, and further provides a uniform distribution of the activeagent over an extended period of time. Nano-particles, due to theirsmall size, have been found to penetrate regions that may beinaccessible from other delivery systems, such as the periodontal pocketareas below the gum line. The use of biodegradable nano-particles asintra-pocket delivery systems also has the advantage that there is noneed to remove them from the treated area.

Bioadhesive substances, also denoted mucoadhesive substances, aregenerally known to be materials that are capable of being bound to abiological membrane and retained on that membrane for an extended periodof time. Compared with conventional controlled release systems,bioadhesive controlled release systems have the following advantages:

i) a bioadhesive controlled release system localizes a biological activeingredient in a particular region, thereby improving and enhancing thebioavailability for active ingredients which may have poorbioavailability by themselves,

ii) a bioadhesive controlled release system leads to a relatively stronginteraction between a bioadhesive substance and a mucosa, such aninteraction contributes to an increasing contact time between thecontrolled release system and the tissue in question and permitslocalization of the active released from the controlled release systemto a specific site,

iii) a bioadhesive controlled release system prolongs delivery ofbiological active ingredients in almost any non-parenteral route,

iv) a bioadhesive controlled release system can be localized on aspecific site with the purpose of local therapy,

v) a bioadhesive controlled release system can be targeted to specificdiseased tissues, and

vi) a bioadhesive controlled release system is useful when conventionalapproaches are unsuitable, such as for certain biological activeingredients which are not adequately absorbed.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference may bemade to the accompanying drawings.

FIG. 1A is an image showing bioadhesion of nano-particles generated byexample II of the detailed description.

FIG. 1B is an image showing bioadhesion of nano-particles generated byexample III of the detailed description.

DETAILED DESCRIPTION

The present invention relates to a controlled release system ofbiologically active ingredients or sensory markers to the oral cavityand mucous membranes of various tissues. Preferably, the controlledrelease system comprises a biologically active ingredient or sensorymarker incorporated into substantially solid nano-particles. Thenano-particles have a hydrophobic core and a positively charged surface.The positively charged surface is formed by a cationic surfactant thatis entrapped and fixed to the particle's surface.

It has now been found that hydrophobic nano-particles having a particlediameter between about 0.01 microns and about 10 microns that comprise apositively charged cation surfactant that is embedded on the surface ofthe particles adhere to biological surfaces of the oral cavity andmucous membranes of various tissues and have the ability to sustain therelease of biologically active ingredients or sensory markers.

I. Nano-Particles

The nano-particle comprises a substantially solid core. Preferably, thesolid core is formed of an inert hydrophobic material.

Preferably, the nano-particles of the present invention have an averagediameter of about 0.01 to about 10 microns. The core of the solidnano-particle contains a biologically active material, such as a drug,anti-septic material antibacterial material, anti-inflammatory, andother such active ingredients that interdict the attachment,propagation, growth or colonization of bacteria on teeth. The core ofthe nano-particle can also include vitamins, zinc, calcium, and thelike. The core of the nano-particle can also contain a sensory marker,such as cooling agents and flavors. The biologically active materials orthe sensory marker can be either hydrophilic or hydrophobic.

The nano particles also comprise a bioadhesive, positively chargedsurfactant. The nano-particles can also include at least oneco-surfactant. The co-surfactant can be a natural biologicallycompatible surfactant or a pharmaceutically acceptable non-naturalsurfactant. The co-surfactant assists in maintaining particles withinthe desired size range and preventing their aggregation. Theco-surfactant comprises less than about 5%, preferably less than about1%, and more preferably less than about 0.1% by weight of thehydrophobic core.

The bioadhesive nano-particles of the present invention are preferablyformed as an aqueous continuous phase suspending a colloidal phase ofsubmicron particles. The aqueous continuous phase of the nano-particlesuspension can contain antioxidants, preservatives, microbicides,buffers, osmoticants, cryoprotectants, and other known pharmaceuticallyuseful additives or solutes.

The nano-particles sustain the release rate of biologically activematerials or sensory markers for an extended period of time. Forexample, the nano-particles sustain the release of biologically activematerials or sensory markers for a period between about ten minutes andabout three months. Preferably the release rate of the nano-particlesfor the biologically active materials can be from about 30 minutes toabout three months and the release rate for the sensory markers can befrom about 10 minutes to about six hours.

The use of nano particles which provide varying rates of diffusion arecontemplated. For example, nano particles may diffuse at any rates ofthe following:

(i) at steady-state or zero-order release ratein which there is asubstantially continuous release per unit of time;

(ii) a first-order release rate in which the rate of release declinestowards zero with time; and

(iii) a delayed release in which the initial rate is slow, but thenincreases with time.

II. Bioadhesive/Mucoadhesive Positively Charged Surfactant

The term “a bioadhesive substance” is broadly defined as a material thatis capable of being bound to a biological membrane and retained on thatmembrane for an extended period of time. The term “bioadhesion” relatesto the attachment of a material to a biological substrate such as abiological membrane. The term “mucoadhesive” is defined as a material inwhich an adhesive bonding is established between a material and themucosa/mucus/mucin of a biological membrane. The term “mucoadhesivesubstance” is in accordance with the generally accepted terminology andis used synonymously with the term “a bioadhesive substance”. Thetemperature referred to as the “melting temperature” is defined as thetemperature at which the solid core material becomes liquid, and thecationic surfactant coating is entrapped and fixed to the particlesurface.

A cationic surfactant is incorporated on an outer surface of thenano-particle to form a bioadhesive nanoparticle. The surfactant isbelieved to be entrapped and fixed to the particle surface and forms acoating at the interface surrounding the particle core. The interfacesurrounding the core is hydrophobic. The cationic surface activematerials are believed to attach to tooth surfaces via a complexinginteraction between the cationic portion of the material and theproteinaceous portion of the tooth for predisposing the surface of thetooth to allow the nano-particles to adhere to the surface of the tooth.The cationic surfactant also stabilizes the outer surface of thehydrophobic core component of the nano-particles, thereby promoting amore uniform particle size.

Surface active materials that are capable of strong bonding to thenegatively charged and hydrophilic surfaces of human teeth arepreferable for use as cationic charged surfactants. Suitable surfaceactive materials include straight-chain alkylammonium compounds, cyclicalkylammonium compounds, petroleum derived cationics, and polymericcationic materials. Cetylpyridinium chloride was found to exhibit strongbioadhesive properties on biological surfaces, and is a preferredsurface active material. The surfactant is present in a proportion ofabout 0.01% to about 5%, preferably about 0.05% to about 2%, by weightof the suspension.

IIa) Straight-chain Alkylammonium Compounds

Straight-chain alkylammonium compounds are cationic surface activematerials in which one or more hydrophobic alkyl groups are linked to acationic nitrogen atom. The linkage can also be more complex as, forexample, in R—CO—NHCH₂CH₂CH₂N(CH₃)₂. Alternatively, the cationic surfaceactive material can contain more than one cationic nitrogen atom such asthe class of compounds of R—NHCH₂CH₂CH₂NH₂ and derivatives thereof.Representative examples of suitable compounds for the cationicsurfactant include: cetyl trimethylammonium chloride (CTAB),hexadecyltrimethylammonium bromide (HDTAB), stearyldimethylbenzylammonium chloride, lauryl dimethylbenzylammonium chloride,cetyl dimethylethylammonium halide, cetyl dimethylbenzylammonium halide,cetyl trimethylammonium halide, dodecyl ethyldimethylammonium halide,lauryl trimethylammonium halide, coconut alkyltrimethylammonium halide,and N,N—C₈₋₂₀-dialkyldimethylammonium halide. Other suitable compoundsfor the cationic surfactant include bis(hydrogenated tallowalkyl)dimethylammonium chloride which is known to adsorb onto thesurface with hydrophobic groups oriented away from it,2-hydroxydodecyl-2-hydroxyethyl dimethyl ammonium chloride andN-octadecyl-N,N′,N′-tris-(2-hydroxyethyl)-1,3-diaminopropanedihydrofluoride.

IIb) Cyclic Alkylammonium Compounds

Surface-active quaternary ammonium compounds in which the nitrogen atomcarrying the cationic charge is part of a heterocyclic ring can be usedas the cationic surfactant. Examples of suitable compounds arelaurylpyridinium chloride, bromide laurylpyridinium,tetradecylpyridinium bromide, and cetylpyridinium halide where thehalide is selected from chloride, bromide or fluoride.

IIc) Petroleum Derived Cationics

Petroleum-based raw materials which can be used as the cationicsurfactant include olefins, paraffins, and aromatic hydrocarbons.Suitable compounds include at least one aliphatic carbon chaincontaining six or more carbon atoms attached to nitrogen. For example,amine salts, diamines, amidoamines, alkoxylated amines, and theirrespective quaternary salts are useful as the cationic surfactant.Preferred petroleum derived compounds of this type include tallow orcoco alkyl substituted 1,3-propylene diamines, such as are manufacturedby Witco under the trade names of “Adogen” and “Emcol” and similardiamines manufactured by Akzo under the trade name “Duomeen” andpolyethenoxy derivatives manufactured under the trade names of“Ethomeen” and “Ethoduomeens”.

IId) Polymeric Amines

Polymeric amines which can be used as the cationic surfactant comprise aclass of polymers containing ionic groups along the backbone chain andexhibit properties of both electrolytes and polymers. These materialscontain nitrogen, of primary, secondary, tertiary or quaternaryfunctionality in their backbone and may have weight average molecularweights as low as about 100 or higher than about 100,000. Suitablepolymeric amines useful as a cationic surfactant include polydimerylpolyamine available from General Mills Chemical Co., polyamide,polyacrylamides, polydiallyldimethylammonium chloride, polyhexamethylenebiguanide compounds, and also other biguanides, for example thosedisclosed in U.S. Pat. Nos. 2,684,924, 2,990,425, 3,183,230, 3,468,898,4,022,834, 4,053,636 and 4,198,425, herein incorporated by referenceinto this application, 1,5-dimethyl-1,5-diazaundecamethylenepolymethobromide, such as “Polybrene” manufactured by Aldrich,polyvinylpyrrolidone and their derivatives, polypeptides,poly(allylamine)hydrochloride, polyoxyethylenated amines, andpolyethyleneimine, such as “Polymin” manufactured by BASF.

Suitable polymeric materials for the cationic surfactant also includesurface active cationic polymers prepared by converting a fraction ofthe amino groups to their acyl derivatives. For example, thepolyethyleneimine is first condensed with less than the stoichiometricquantity of acid halides thus alkylating some of the amino groups andthe remaining amino groups are then condensed with hydrogen halides suchas hydrogen chloride or, preferably, hydrogen fluoride. The surfaceactivity of these compounds varies with the number of amino groups whichare acylated and with the chain length of the acylating group RCO. Thecondensation reaction can be performed with stearic or oleic acidchlorides in the presence of a solvent containing metal fluoride,preferably silver fluoride, in such a manner that metal chloride formedin the reaction precipitates from the solvent.

Also suitable, for the purpose of this invention, are cationicderivatives of polysaccharides such as dextran, starch or cellulose, forexample, diethylaminoethyl cellulose. Examples of applicable copolymersbased on acrylamide and a cationic monomer are available from HerculesInc. under the trade name RETEN including RETEN 220, or from NationalAdhesives under the trade name FLOC AID including FLOC AID 305. Otheruseful acrylamide-based polyelectrolytes are available from AlliedColloids under the trade name PERCOL. Further examples of suitablematerials are cationic guar derivatives such as those sold under thetrade name JAGUAR by Celanese-Hall.

Another further preferred group of compounds suitable for the cationicsurfactant which comprises a class of water-insoluble polymers, havingnitrogen atoms in their molecules, include quaternary polymers ofquaternary ammonium type, betaine type, pyridylpyridinium type orvinylpyridinium-type. Examples of this group of compounds are:poly(vinyl-benzylmethyllaurylammonium chloride),poly(vinyl-benzylstearylbetaine),poly(vinyl-benzyllaurylpyridylpyridinium chloride),poly(vinyl-benzylcetylammonylhexyl ether) and quaternizedpolyoxyethyleneated long chain amines having the formulaRN(CH₃)[(C₂H₄O)_(x)H]₂(+)A(−), where A(−) is generally chloride orfluoride, x is a number from 1 to 20, and R is C₈₋₂₂-alkyl.

A strongly ionic bond is produced upon reacting the above describedcationic surfactants with dental surfaces.

III. Core Hydrophobic Barrier Materials

The nanoparticle hydrophobic core is preferably formed of abiodegradable hydrophobic materials having barrier properties. The term“degradable material”, as used herein, means a material which degradeswithin three months when placed in the mouth of a typical patient. Thematerials degrade as a result of exposure to one or more enzymes thatcommonly are found in the mouth. These enzymes include lipases,proteases, and glucosidases.

Suitable, nontoxic, pharmaceutical solid core materials are inerthydrophobic biocompatible materials with a melting range between about50 degrees and about 120 degrees C. Examples are natural, regenerated,or synthetic waxes including: animal waxes, such as beeswax; lanolin andshellac wax; vegetable waxes such as carnauba, candelilla, sugar cane,rice bran, and bayberry wax; mineral waxes such as petroleum waxesincluding paraffin and microcrystalline wax; cholesterol; fatty acidesters such as ethyl stearate, isopropyl myristate, and isopropylpalmitate; high molecular weight fatty alcohols such as cetostearylalcohol, cetyl alcohol, stearyl alcohol, and oleyl alcohol; solidhydrogenated castor and vegetable oils; hard paraffins; hard fats;biodegradable polymers such as polycaprolactone, polyamides,polyanhydrides, polycarbonates, polyorthoesters, polylactic acids, andcopolymers of lactic acid and glycolic acid; cellulose derivatives andmixtures thereof. Other hydrophobic compounds which may be used in thepresent invention include triglycerides, preferably of food grade purityor better, which may be produced by synthesis or by isolation fromnatural sources. Natural sources may include animal fat or vegetableoil, such as, soy oil, a source of long chain triglycerides (LCT). Othersuitable triglycerides are composed predominantly of medium length fattyacids (C10-C18), denoted medium chain triglycerides (MCT). The fattyacid moieties of such triglycerides can be unsaturated, monounsaturatedor polyunsaturated. Mixtures of triglycerides having various fatty acidmoieties are also useful for the present invention. The core cancomprise a single hydrophobic compound or a mixture of hydrophobiccompounds. Hydrophobic materials are known to those skilled in the artand are commercially available, as described in the list of suitablecarrier materials in Martindale, The Extra Pharmacopoeia, ThePharmaceutical Press, 28th Edition pp 1063-1072 (1982). Considerationsin the selection of the core material include good barrier properties tothe active ingredients and sensory markers, low toxicity and irritancy,biocompatibility, stability, and high loading capacity for the activeingredients of interest.

IV. Co-Surfactant

An amphiphilic or nonionic co-surfactant can be used in thenanoparticles of the present invention to provide improved stability.Co-surfactants can be formed of natural compounds or nonnaturalcompounds. Examples of natural compounds are phospholipids and cholates.Examples of nonnatural compounds include: polysorbates, which are fattyacid esters of polyethoxylated sorbitol sold by Unigema surfactants asTween; polyethylene glycol esters of fatty acids from sources such ascastor oil; polyethoxylated fatty acid, such as stearic acid;polyethoxylated isooctylphenol/formaldehyde polymer; poloxamers, suchas, poly(oxyethylene)poly(oxypropylene) block copolymers available fromBASF as Pluronic; polyoxyethylene fatty alcohol ethers available fromICI surfactants as Brij; polyoxyethylene nonylphenyl ethers sold byUnion Carbide as Triton N; polyoxyethylene isooctylphenyl ethers sold byUnion Carbide as Triton X; and SDS. Mixtures of surfactant molecules,including mixtures of surfactants of different chemical types, can beused in the present invention. Surfactants preferably are suitable forpharmaceutical administration and compatible with the drug to bedelivered.

Particularly suitable surfactants include phospholipids, which arehighly biocompatible. Especially preferred phospholipids arephosphatidylcholines (lecithins), such as soy or egg lecithin. Othersuitable phospholipids include phosphatidylglycerol,phosphatidylinositol, phosphatidylserine, phosphatidic acid,cardiolipin, and phosphatidylethanolamine. The phospholipids may beisolated from natural sources or prepared by synthesis. Phospholipidsurfactants are believed to usually form a single monolayer coating ofthe hydrophobic core.

The co-surfactant can be present in an amount less than about 5%,preferably less than about 1%, and more preferably less than about 0.1%,relative to the weight of hydrophobic core component. In someembodiments, one or more co-surfactants can be used.

V. Biologically Active Ingredients

It has been found that streptococcus mutans, and streptococcus sobrinus,are the bacteria shown to be major sources of bacterial plaque coloniesand their sequelae. The types of materials that inhibit or defeat theattachment or propagation, growth or colonization of bacteria on dentalsurfaces are various cetyl amines, nitroparaffin derivatives, duomeens,ethoxylated duomeens, and other quaternary ammonium compounds.Especially useful is5-Amino-1,3-bis(2-ethylhexyl)-5-methylhexahydropyrimidine, such areavailable from Angus Chemical Co. by the trade name hexetidine.Descriptions of other suitable drugs within these therapeuticclassifications illustratively can be found in Goodman and Gilman'sPharmacological Basis of Therapeutics, eighth edition (1990).

Biologically active ingredient in the present invention can also includean effective amount of an anticalculus agent. An effective amount, asused herein, is any amount of an anticalculus agent sufficient to beeffective in reducing calcium phosphate mineral deposition related tocalculus formation. Suitable anticalculus agents include pyrophosphatesalts such as the dialkali metal pyrophosphate salts, tetra alkali metalpyrophosphate salts, and mixtures thereof. Disodium dihydrogenpyrophosphate (Na₂H₂P₂O₇), tetrasodium pyrophosphate (Na₄P₂O₇), andtetrapotassium pyrophosphate (K₄P₂O₇) in their unhydrated as well ashydrated forms are the preferred species. In compositions of the presentinvention, the pyrophosphate salt can be present in one of three ways:substantially dissolved, substantially undissolved, or a mixture ofdissolved and undissolved pyrophosphate.

Compositions comprising substantially dissolved pyrophosphate refer tocompositions where at least one pyrophosphate ion source is present inan amount sufficient to provide at least about 1.0% free pyrophosphateions. The amount of free pyrophosphate ions can be from about 1% toabout 15%, preferably from about 1.5% to about 10%, and most preferablyfrom about 2% to about 6%, by weight of the composition. Freepyrophosphate ions can be present in a variety of protonated statesdepending on a the pH of the composition.

Compositions comprising substantially undissolved pyrophosphate as theanticalculus agent refer to compositions containing no more than about20% of the total pyrophosphate salt dissolved in the composition,preferably less than about 10% of the total pyrophosphate dissolved inthe composition. Tetrasodium pyrophosphate can be in the anhydrous saltform or the decahydrate form or as any other species stable in solidform in the dentifrice compositions. The pyrophosphate salt is in itssolid particle form, which can be its crystalline or amorphous state,with the particle size of the salt preferably being small enough to beaesthetically acceptable and readily soluble during use. The amount ofpyrophosphate salt useful in making these compositions is any tartarcontrol effective amount. The effective amount can be about 1.5% toabout 15%, preferably from about 2% to about 10%, and most preferablyfrom about 2.5% to about 8%, by weight of the composition. Some or allof the tetrasodium pyrophosphate can be undissolved in the product andpresent as tetrasodium pyrophosphate particles. Pyrophosphate ions indifferent protonated states such as, H P₂O₇ ⁻³ can be present dependingupon the pH of the composition and if a portion of the tetrasodiumpyrophosphate is dissolved.

A mixture of dissolved and undissolved pyrophosphate salts can comprisea mixture of any of the above described pyrophosphate salts. Suitableexamples of pyrophosphate salts useful for practice of the presentinvention are also described in more detail in Kirk & Othmer,Encyclopedia of Chemical Technology, Fourth Edition, Volume 18,Wiley-Interscience Publishers (1996), incorporated herein by referencein its entirety, including all references incorporated into Kirk &Othmer.

Other anticalculus agents which can be used instead of the pyrophosphatesalt of or in combination with the pyrophosphate salt include suchmaterials known to be effective in reducing calcium phosphate mineraldeposition related to calculus formation. Suitable anticalculus agentsinclude synthetic anionic polymers including: polyacrylates andcopolymers of maleic anhydride or acid and methyl vinyl ether availablefrom ISP Technologies Inc. as Gantrez, such as described, for example,in U.S. Pat. No. 4,627,977, the disclosure of which is incorporatedherein by reference in its entirety; polyamino propane sulfonic acid(AMPS); zinc citrate trihydrate; diphosphonates, such as EHDP and AHP;polypeptides, such as polyaspartic and polyglutamic acids, and mixturesthereof. Polyphosphates can also be used as an anticalculus agent.Polyphosphate is generally understood to consist of two or morephosphate molecules arranged primarily in a linear configuration,although some cyclic derivatives may be present. Inorganic polyphosphatesalts include tetrapolyphosphate and hexametaphosphate. Polyphosphateslarger than tetrapolyphosphate usually occur as amorphous glassymaterials. Examples of polyphosphates are manufactured by FMCCorporation as Sodaphos, Hexaphos, and Glass H and are described in moredetail in Kirk & Othmer, Encyclopedia of Chemical Technology, FourthEdition, Volume 18, Wiley-Interscience Publishers (1996), incorporatedherein by reference in its entirety, including all referencesincorporated into Kirk & Othmer.

Other biologically active ingredients useful to counter bacterialattachment and plaque formation are anti-microbial. Preferredanti-microbial agents include, triclosan, phenolic compounds which canbe monomeric or polymeric, synthetic or natural; nature-derivedanti-microbials such as sanguinarine; cetylpyridinium salts;benzalkonium salts; benzethonium salts; domiphen salts; bisbiguanides,such as chlorhexidene; bisbiguanide salts; phosphonium salts; ammoniumsalts; peroxides and other oxidants; zinc salts; and antibiotics such aspenicillin, vancomycin, kanamycin, erythromycin, niddamycin, spiramycin,tetracycline, minocycline, and metronidazole. Particularly preferredanti-microbial agents include triclosan, chlorhexidene or an acceptablesalt of chlorhexidene. When chlorhexidene is selected as theanti-microbial agent, the controlled delivery process of the inventionresults in a reduction of undesirable side effects, such as staining ofthe teeth and tongue. It has been found that, when the particles of thepresent invention are composed of a degradable material and ananti-microbial agent, substantially nothing remains of the particles inthe mouth or body once the degradable material degrades and all of theanti-microbial agent is released. A particularly preferredanti-microbial agents are an anti-bacterial compound which contains twobiguanide moieties, such as triclosan and chlorhexidene, each attachedin the para position to a separate chlorophenyl group, and joined by ahexane linkage (see, for example, Rose et al., J. Chem Soc., p. 4422(1956) and U.S. Pat. No. 2,684,924). Pharmaceutically acceptable saltsof chlorhexidene, such as chlorhexidene gluconate, chlorhexidenediacetate, chlorhexidene dihydrochloride, chlorhexidene dihydrofluoride,and chlorhexidene dihydrobromide can also be used in the presentinvention. Chlorhexidene and its associated salts are commerciallyavailable. The gluconate salt can be purchased, for example, as a 20.5percent w/w aqueous solution from Pliva Pharmaceutical of Zagreb,Yugoslavia, and from ICI Ltd. of England. Chlorhexidene gluconate as afreeze-dried solid is available from Pliva Pharmaceutical.

Suitable drugs which can be administered in the drug delivery system ofthe present invention include: anti-bacterial agents such as thimerosal,chloramine, boric acid, phenol, iodoform, chlorhexidine and other oralantiseptics; beta-lactam antibiotics, for example cefoxitin,n-formamidoyl thienamycin and other thienamycin derivatives,tetracyclines, chloramphenicol, neomycin, gramicidin, kanamycin,amikacin, sismicin and tobramycin; anti-inflammatory steroids such ascortisone, hydrocortisone, beta-methasone, dexamethasone, fluocortolone,prednisolone, triamcinolone and the like; non-steroidalanti-inflammatory drugs including flurbiprofen, ibuprofen, indomethacin,piroxicam, naproxen, antipyrine, phenylbutazone and aspirin; plaquedissolving substances, for example lysozyme chloride or amylase; andlocal anaesthetics such as lidocaine, procaine, benzocaine, xylocaineand the like. It will be appreciated that other conventionalanti-bacterial agents can be incorporated into the present invention.The biologically active ingredient can also be one or more antibiotics,such as penicillin, polymyxin B, vancomycin, kanamycin, erythromycin,niddamycin, metronidazole, spiramycin and tetracycline.

The compositions of the present invention can further comprise a sourceof calcium ions selected from the group of calcium salts, calciumsulfate, calcium phosphate, calcium acetate, calcium formate, calciumlactate, calcium nitrate and mixtures thereof.

The compositions of the present invention can further comprise a sourceof zinc. For example, the source of zinc can be selected from the groupof zinc acetate, zinc ammonium sulfate, zinc benzoate, zinc bromide,zinc borate, zinc citrate, zinc chloride, zinc gluconate, zincglycerophosphate, zinc hydroxide, zinc iodide, zinc oxide, zincpropionate, zinc D-lactate, zinc DL-lactate, zinc pyrophosphate, zincsulfate, zinc nitrate, and zinc tartrate.

The compositions of the present invention can further comprise a sourceof fluoride. Suitable sourcing of fluoride include sodium fluoride,potassium fluoride, tin fluoride, zinc fluoride, organic fluorides suchas long-chained aminofluorides, for example oleylaminofluoride, cetylaminofluoride or ethanolaminohydrofluoride, fluorosilicates, forexample, potassium hexafluorosilicate or sodium hexafluorosilicate,fluorophosphates such as ammonium, sodium, potassium, magnesium orcalcium fluorophosphate and fluorozirconates, for example sodium,potassium or tin fluorozirconate.

Cetylpyridinium chloride is biologically active ingredient that possesboth anti-bacterial activity and bioadhesive/mucoadhesive surfaceactivity. Other materials having these properties which can be used inthe present invention include are described in: U.S. Pat. Nos.2,984,639, 3,325,402, 3,431,208, and 3,703,583, and British Patents No.1,319,396 hereby incorporated by reference in their entirety into thisapplication.

VI. Sensory Marker

The present invention provides for synchronization of the release of thesensory markers such as flavors and cooling agents with that of theactive antibacterial agent. The release of the sensory markers can beused to convey to the consumer the product performance, provide longlasting freshness, and signal to the consumer that a new application ofthe product is needed. It has been found that many consumers wouldprefer for the flavor present in oral care product to remain in themouth for an extended period of time to convey a lasting impression offreshness.

It will be understood herein that a flavoring composition is one capableof imparting a definite flavor to a tasteless or bland foodstuff. Aflavor-enhancing composition is understood to be one capable ofreinforcing one or more flavor notes of a natural or other materialwhich is deficient in flavor. A flavor-enhancing composition would beuseful for improving the flavor of, for example, a meat product, theflavor of which was diminished or undesirably altered by processing.Flavoring compositions can include flavoring ingredients, carriers,vehicles and the like to form compositions suitable for imparting aflavor to, enhancing the flavor in, or altering the flavor of a productcomposition.

Flavoring compositions used in the present invention can be used toenhance existing flavors in or to provide the entire flavor impressionto a foodstuff. Suitable flavoring compositions can include organicacids, including fatty, saturated, unsaturated and amino acids;alcohols, including primary and secondary alcohols, esters, carbonylcompounds including aldehydes and ketones, lactones, cyclic organicmaterials including benzene derivatives, alicyclics, heterocyclics suchas furans, pyridines, pyrazines and the like; sulfur-containingmaterials including thiols, sulfides, disulfides and the like, proteins,lipids, carbohydrates; and flavor potentiators such as monosodiumglutamate, guanylates, inosinates, and natural flavoring materials suchas vanillin, and the like. It will be appreciated that the types andamounts of materials selected from the foregoing groups of materialswill depend upon the precise organoleptic character desired in thefinished product and, especially in the case of flavoring compositionsused to enhance other flavors, will vary according to the foodstuff towhich the flavor and aroma are to be imparted. Inorganic materials suchas sodium chloride and freshness preservers such as butylatedhydroxyanisole, butylated hydroxytoluene and propyl gallate can be addedfor their adjuvant preservative effects on the flavoring composition oron the final food composition itself. Typical examples of usable flavorcompounds useful for practice of the present invention are described inS. Arctander, Perfume and Flavor Chemicals, Montclair, N.J., (USA)(1969).

VII. Processing Method of the Nano-Particles

The nano-particles of the present invention can be made by numerousconventional, well-known methods. Particle-making procedures aredescribed generally in Nixon (ed.), Microencapsulation, pp. 13-38(Marcel Dekker, Inc. 1976); Muller, Colloidal Carriers for ControlledDrug Delivery and Targeting, pp. 175-202 (CRC Press 1991); Shaw (ed.),Lipoproteins as Carriers of Pharmacological Agents, pp. 97-139 (MarcelDekker, Inc. 1991); and Benita (ed.), Microencapsulation—Methods andIndustrial applications, pp. 183-258 (Marcel Dekker, Inc. 1996).

A process for producing the nano-particles can comprise the followingsteps:

heating the hydrophobic core material to a temperature above thematerial melting point;

dissolving or dispersing the active ingredients or the sensory markerinto the melt;

dissolving or dispersing the positively charged surfactant or theco-surfactant in the aqueous phase and heating it to a temperature abovethe melting point of the melt;

mixing the melt with an aqueous solution to form a suspension;

high shear homogenization of the suspension at a temperature above themelting temperature until a homogeneous fine suspension is obtained; and

rapidly cooling the suspension to below the melting point of the corematerial mixture composed of the hydrophobic materials, activeingredients, or sensory markers, to form a fine dispersion. Preferably,the fine dispersion is uniform and milky.

The method of preparation of nano-particles described herein ischaracterized by high loading, reproducibility, versatility, andstability. The method is further illustrated in the non-limitingexamples.

VIII. Bioadhesion Measurements

The oral cavity is lined by non-keratinizd, stratified, squamousepithelial cells. This type of epithelial cells also lines other softtissue surfaces that include esophagus, vagina and cervix. A HeLa cellline that has been used to determine the bioadhesive/mucoadhesiveproperties of the nano-particles of the present invention is anepithelial-like cell line, originally derived from a carcinoma of thecervix. HeLa cells are cultured in Minimal Essential Medium (Eagles)with 10% fetal bovine serum. To test the adherence of nano-particles tothe cell surface, HeLa cells are being plated at a density of 2×10⁵cells per dish (35 mm) in 2 ml medium. Three dishes are seeded for eachdata point. On the following day, the particles are being dispersed in 1ml medium. The medium in which the cells are cultured is aspirated andreplaced immediately with the nano-particles-containing medium. Theparticles are left to adhere to the cells by gravity for time periodssuch as 5 minutes, 15 minutes, and 30 minutes. At each time point themedium is aspirated, and the cells surface are gently rinsed twice with2 ml medium, simulating rinsing the mouth following brush. Cells areimaged immediately using an Olympus IX-70 inverted fluorescentmicroscope and Princeton Instruments Micromax cooled CCD camera. Theimages are saved and stored and analyzed using the IPLab ScientificImaging Software (Scanalytics, Inc, Va.) to determine the number ofparticles adherent to the cells per field. Images from three randomfields are collected from each dish. Each experiment generates a totalof nine data points, for each time point. The nine data points areaveraged. Each experiment is repeated at least 3 times. Results obtainedfrom three or more independent experiments are averaged and expressed asa mean±standard deviation (SD). The data are subjected to statisticalanalysis using the StatView program using Student's t-test method todetermine whether the difference among groups is statisticallysignificant. Results are accepted as significant when p<0.05.

The ability of the nano-particles of the present invention describedbelow to adhere to HeLa cultured cells is shown in FIGS. 1A and 1B.FIGS. 1A and 1B show specific adhestion of nanoparticles to HeLa cells.FIG. 1A shows bioadhesion of the nanoparticles described in example II.FIG. 1B shows the bioadhesion of the nanoparticles described in ExampleIII. FIGS. 1A-1B indicate that adhesion of the nanoparticles to the HeLacells is clearly evident.

IX. Oral Hygiene Products

The biodegradable bioadhesive nano-particles provided by the presentinvention can generally be incorporated into any suitable conventionaloral hygiene product. Exemplary delivery systems include gels, chewinggums, toothpaste, and mouthwash. The toothpaste can include otherconventional components such as an abrasive such as, silica or alumina,having a particle size of between about 5 microns and about 50 microns,a thickener such as, colloidal silica having a particle size of betweenabout 0.1 microns and about 1 micron, and neat flavor oil. The oralhygiene product can be appropriately selected depending upon thephysical location for delivery of the nano-particles and the intendeduse of the nano-particles. The above-described exemplary deliverysystems are preferred in accordance with the present invention, sincethey permit effective delivery of the bioadhesive nano-particles intothe oral cavity.

The invention is illustrated by the following, non-limiting, examples,in which the abbreviations have the meanings commonly used in the art.The following examples illustrate embodiments of this invention. Allparts, percentages and proportions referred to herein and in theappended claims are by weight, unless otherwise indicated.

EXAMPLE I Preparation of Nano-Particles with Menthol and CetylpyridiniumChloride (CPC)

The following procedure is used for the preparation of nano-particleswith menthol as sensory marker and cetylpyridinium chloride (CPC) asboth the biologically active ingredient and bioadhesive/mucoadhesivesurfactant. The hydrophobic core of the nano-particles in composed ofcandelilla wax and the suspension is homogenized using a high speedhomogenizer (T25basic IKA Labortechnik, IKA Works Inc, Wilmington N.C.,Cole-Palmer.

60 grams of candelilla wax is placed in an oven at 80 degrees C. andallowed to melt. 298 grams of water are placed into a one liter glassbeaker, and 4 grams of CPC are added to the water. The aqueous solutionand is heated to 90 degrees C. on a hot plate. When the aqueous solutionreaches 90 degrees C. the solution is mixed with the homogenizer.Candelilla wax is removed from the oven and 40 grams of menthol crystalsare mixed into the wax by hand with a glass rod. The menthol/wax mixtureis poured into the beaker containing the aqueous solution and theemulsion is homogenized at 24,000 rpm for 50 seconds. The uniformmilk-like formulation was immediately cooled to room temperature byimmersing the beaker into an ice/water bath with continued mixing. Theresulting formulation is:

74% water;

15% candelilla wax;

10% flavor; and

1% Cetylpyridinium chloride (CPC).

The microcapsules of Example I were subjected to in vitro bioadhesionmeasurements, utilizing the technique previously described. Measurementsof the adhesion of particles to cells were carried out on thenano-particles of Example I, along with the appropriate controls, usingcultured human epithelial HeLa cells as a model system as describedpreviously. The nano-particles of Example I were observed to exhibitexcellent bioadhesive properties the cultured cells HeLa cells.

EXAMPLE II Preparation of Nano-Particles with Menthol andCetylpyridinium Chloride (CPC)

The following procedure is used for the preparation of nano-particleswith menthol as sensory marker and cetylpyridinium chloride (CPC) asboth the biologically active ingredient and bioadhesive/mucoadhesivesurfactant. The hydrophobic core of the nano-particles in composed ofcandelilla wax and the suspension is homogenized using a Silverson L4Rlaboratory mixer.

60 grams of candelilla wax is placed in an oven at 80 degrees C. andallowed to melt. 298 grams of deionized water is placed into a onegallon vessel fitted with a all-purpose silicon rubber heater(Cole-Palmer Instrument Company) and 4 grams of CPC were added to thewater. The aqueous solution is heated to 90 degrees C. with constantmixing using a propeller mixer. Candelilla wax is removed from the ovenand 40 grams of menthol crystals are mixed into the wax by hand with aglass rod. The menthol/wax mixture is poured into the vessel containingthe aqueous solution and the emulsion is homogenized at maximum speedfor 50 seconds using a Silverson in-line model L4R laboratoryrotor/stator mixer. The emulsion is cooled to ambient temperature bypassing it through a tube-in-tube heat exchanger (Model 00413, ExergyInc. Hanson Mass.). The resulting formulation is:

74% water;

15% candelilla wax;

10% menthol; and

1% Cetylpyridinium chloride (CPC).

The shape and size of the nano-particles was verified by examining thesamples under a scanning electron microscope (SEM). SEM studies showedthat the nano-particles of Example II were spherical in nature with anaverage particle size of approximately 1 micron. The microcapsules ofExample II were subjected to in vitro bioadhesion measurements,utilizing the technique previously described. Measurements of theadhesion of particles to cells were carried out on the nano-particles ofExample II, along with the appropriate controls, using cultured humanepithelial HeLa cells as a model system as described previously. Thenano-particles of Example II were observed to exhibit excellentbioadhesive properties the cultured cells HeLa cells.

EXAMPLE III Preparation of Nano-Particles with Menthol andCetylpyridinium Chloride (CPC)

The following procedure is used for the preparation of nano-particleswith menthol as sensory marker and cetylpyridinium chloride (CPC) asboth the biologically active ingredient and bioadhesive/mucoadhesivesurfactant. The hydrophobic core of the nano-particles in composed ofcandelilla wax and the suspension is homogenized using an APV, Rannie2000 High Pressure Homogenizer.

60 grams of candelilla wax is placed in an oven at 80 degrees C. andallowed to melt. 298 grams of deionized water is placed into the onegallon vessel of the homogenizer, that fitted with a all-purpose siliconrubber heater (Cole-Palmer Instrument Company). 4 grams of CPC are addedto the water and the aqueous solution is heated to 90 degrees C. whilemixing it with a propeller mixer. Candelilla wax is removed from theoven and 40 grams of menthol crystals are mixed into the wax by handwith a glass rod. The menthol/wax mixture is poured into the vesselcontaining aqueous solution and the emulsion is homogenized at 20,000psi. The emulsion is cooled to ambient temperature by passing it througha tube-in-tube heat exchanger (Model 00413, Exergy Inc. Hanson Mass.).The resulting formulation is:

74% water;

15% candelilla wax;

10% menthol; and

1% Cetylpyridinium chloride (CPC).

The shape and size of the nano-particles was verified by examining thesamples under a scanning electron microscope (SEM). SEM studies showedthat the nano-particles of Example III were spherical in nature with anaverage particle size of approximately 0.1 microns.

The microcapsules of Example III were subjected to in vitro bioadhesionmeasurements, utilizing the technique previously described. Measurementsof the adhesion of particles to cells were carried out on thenano-particles of Example III, along with the appropriate controls,using cultured human epithelial HeLa cells as a model system asdescribed previously. The nano-particles of Example III were observed toexhibit excellent bioadhesive properties the cultured cells HeLa cells.

EXAMPLE IV

The preparation procedures disclosed in Examples I through III areduplicated for the preparation of nano-particles with menthol as sensorymarker, zinc citrate as the biologically active ingredient, andcetylpyridinium chloride (CPC) as bioadhesive/mucoadhesive surfactant.The formulation of the resulting suspension is:

72.5% water;

10% candelilla wax;

5% zinc citrate;

5% menthol; and

1% Cetylpyridinium chloride (CPC).

The microcapsules of Example IV were subjected to in vitro bioadhesionmeasurements, utilizing the technique previously described. Measurementsof the adhesion of particles to cells were carried out on thenano-particles of Example IV, along with the appropriate controls, usingcultured human epithelial HeLa cells as a model system as describedpreviously. The nano-particles of Example IV were observed to exhibitexcellent bioadhesive properties the cultured cells HeLa cells.

EXAMPLE V

The preparation procedures disclosed in Examples I through III areduplicated for the preparation of nano-particles with a flavor assensory marker, zinc citrate as the biologically active ingredient,cetylpyridinium chloride (CPC) as bioadhesive/mucoadhesive surfactant,and Tween 80, as co-surfactant. The formulation of the resultingsuspension is:

72% water;

10% candelilla wax;

5% zinc citrate;

5% double mint flavor (Noville);

1% Cetylpyridinium chloride (CPC); and

0.5% Tween 80

The microcapsules of Example V were subjected to in vitro bioadhesionmeasurements, utilizing the technique previously described. Measurementsof the adhesion of particles to cells were carried out on thenano-particles of Example V, along with the appropriate controls, usingcultured human epithelial HeLa cells as a model system as describedpreviously. The nano-particles of Example V were observed to exhibitexcellent bioadhesive properties the cultured cells HeLa cells.

The nano-particles produced in Examples I to V, exhibit excellentbioadhesive properties, permit the sustained release of the sensorymarker over extended period of time, when used in oral hygienepreparation in accordance with the use of Examples: U.S. Pat. Nos.6,090,402, 6,071,500, and 6,045,780, each of which is herebyincorporated by reference into this application.

EXAMPLE VI Use of Mouth Rinse

10 grams of the suspension of Example III is admixed with 90 grams of amouth rinse composition, as described in U.S. Pat. No. 6,090,402containing: An anti-plaque dental rinse similar to that described inExample 4 of U.S. Pat. No. 4,666,708 is formulated from the followingcomponents combined in the weight percentages tabulated below:

2.00% (weight) Sodium benzoate

0.20% (weight) Sodium salicylate

0.50% (weight) Sodium Bicarbonate

0.20% (weight) Sodium Borate

0.50% (weight) Sodium lauryl sulfate

0.80% (weight) Polysorbate 20

0.02% (weight) Sodium saccharin

15.00% (weight) Glycerol

7.00% (weight) Ethanol, 95%

Water to 100%

The mouth rinse comprising the nano-particles is applied to the teeth byrinsing the teeth with 100 grams of the mouth rinse comprising thenano-particles and rinsing the teeth with 50 ml. of water two times.Menthol perception in the mouth following the application of the productcomprising the nano-particles vs. toothpaste comprising an equivalentamount of neat menthol, was evaluated organoleptically. A panel test wasconducted to determine which product provides the strongest perceptionof menthol (using a scale of 0-10), after 10 minutes, 1 hour, and 3hours following application of the product with the following results:

Menthol Intensity (a scale of 1-10) 10 minutes 1 Hour 3 Hours MouthRinse of neat menthol 3 1 1 Mouth rinse of menthol/nano-particles 6 4 3

The mouth rinse containing the nano-particles provided a higherintensity of menthol for an extended period of time, compared to thesample containing the neat menthol. It was readily apparent that themouth rinse containing the inventive nano-particles provided longerlasting menthol perception.

EXAMPLE VII Use of Toothpaste

10 grams of the suspension of Example III is admixed with 90 grams of atoothpaste composition, as described in U.S. Pat. No. 6,045,780containing:

22.00% (weight) Glycerine

49.00% (weight) Dicalcium phosphate

2.00% (weight) Sodium lauryl sulfate

0.20% (weight) Sodium saccharin

0.50% (weight) Sodium benzoate

0.75% (weight) Sodium monofluorophosphate

0.25% (weight) Tetrasodium pyrophosphate

0.60 to 1.00% (weight) Combination viscosity builder

Color and flavor oil to suit

Water to 100.00%

The toothpaste composition can be prepared on a small scale bydispersing a dry blend of the sodium saccharin, sodium benzoate,tetrasodium pyropyosphate, sodium monofluorophosphate, and combinationviscosity builder into a beaker containing the glycerine. This is mixedfor 5 minutes and then water is added. The mixture is heated to 65-71degree C. in a boiling water bath and the temperature held for 20minutes, compensating for evaporated water loss. The mixture is thentransferred to a Ross mixer. The dicalcium phosphate is added, using aspatula. The formulation is then mixed at speed 2 for 2 minutes, whenthe mixer is stopped and the bowl and blades are scraped. Mixing isresumed at speed 5-6 for 15 minutes with a vacuum of not less than 28inches Hg. The sodium lauryl sulfate and flavor oil are then added withmixing at speed 2 for 3 minutes under vacuum.

The toothpaste comprising the nano-particles is applied to the teeth bybrushing the teeth with 1 gram of the toothpaste comprising thenano-particles and rinsing the teeth with 50 ml. water two times.Menthol perception in the mouth following the application of the productcomprising the nano-particles vs. toothpaste comprising an equivalentamount of neat menthol, was evaluated organoleptically. A panel test isconducted to determine which product provides the strongest perceptionof menthol (using a scale of 0-10), after 10 minutes, 1 hour, and 3hours following application of the product

Menthol Intensity (a scale of 1-10) 10 minutes 1 Hour 3 Hours Toothpasteof neat menthol 2 1 1 Toothpaste of the menthol/nano- 6 5 2 particles

The toothpaste containing the nano-particles provided a higher intensityof menthol for an extended period of time, compared to the samplecontaining the neat menthol. It was readily apparent that the toothpastecontaining the inventive nano-particles provided longer lasting mentholperception.

EXAMPLE VII Use of Breath Spray

10 grams of the suspension of Example III is admixed with 90 grams of abreath spray composition, as described in U.S. Pat. No. 6,071,500containing:

79.26% (weight) Purified Water

0.02 (weight) Ascorbic Acid (Vit C)

0.05% (weight) Zinc Glucomate

0.01% (weight) Echinacea

0.55% (weight) Spearmint

20% (weight) XYLITOL

0.01% (weight) Sodium Benzoate

0.10% Calcium Hydroxide

The breath spray comprising the nano-particles is applied to the teethby spraying the teeth with 0.5 grams of the breath spray comprising thenano-particles. Menthol perception in the mouth following theapplication of the product comprising the nano-particles vs. a breathspray comprising an equivalent amount of neat menthol, was evaluatedorganoleptically. A panel test is conducted to determine which productprovides the strongest perception of menthol (using a scale of 0-10),after 10 minutes, 1 hour, and 3 hours following application of theproduct

Menthol Intensity (a scale of 1-10) 10 minutes 1 Hour 3 Hours Breathspray of neat menthol 3 1 1 Breath spray of the menthol/nano- 7 5 3particles

The breath spray containing the nano-particles provided a higherintensity of menthol for an extended period of time, compared to thesample containing the neat menthol. It was readily apparent that thebreath spray containing the inventive nano-particles provided longerlasting menthol perception.

It is understood that the above-described embodiments are illustrativeof only a few of the many possible specific embodiments which canrepresent applications of the principles of the invention. Numerous andvaried other arrangements can be readily derived in accordance withthese principles by those skilled in the art without departing from thespirit and scope of the invention.

What is claimed is:
 1. A controlled release delivery system for delivery to biological surfaces comprising an oral cavity or mucous membranes of various tissues, said system comprising: a plurality of solid nano-particles, each of said solid nano-particles comprising a core formed of a hydrophobic material selected from the group consisting of natural waxes, synthetic waxes, fatty acid esters, fatty alcohols, solid hydrogenated plant oils, biodegradable natural polymers and synthetic polymers, and an effective amount of a first active agent contained therein and a bioadhesive positively charged surfactant entrapped on a surface of each of said solid nano-particles surrounding said core, wherein said positively charged surfactant is selected from the group consisting of straight-chain alkylammonium compounds, cyclic alkylammonium compounds, petroleum derived cationics, and polymeric cationic materials.
 2. The system of claim 1 wherein said hydrophobic material has a melting point between 50 degrees C. and 120 degrees C.
 3. The system of claim 1 wherein said hydrophobic material comprises candelilla wax.
 4. The system of claim 1 wherein said first active agent is a biologically active agent selected from the group consisting of anti-septic materials, antibacterial materials, anti-inflammatory materials and active ingredients that interdict the attachment, propagation, growth and or colonization of bacteria on teeth.
 5. The system of claim 1 wherein the first active agent is an antibacterial agent selected from the group consisting of thimerosal, chloramine, boric acid, phenol, iodoform, chlorhexidine, oral antiseptic, beta-lactam antibiotic, cefoxitin, n-formamidoyl thienamycin, thienamycin derivatives, tetracycline, chloramphenicol, neomycin, gramicidin, kanamycin, amikacin, sismicin and tobramycin.
 6. The system of claim 1 wherein said first active agent is a sensory marker selected from the group consisting of a flavor and cooling agent.
 7. The system of claim 1 wherein said first active agent is a biological active agent and further comprising a second active agent, said second active agent is a sensory marker.
 8. The system of claim 7 wherein a release rate of said first active agent is synchronized with a release rate of said second active agent.
 9. The system of claim 1 wherein said positively charged surfactant is cetylpyridinium chloride.
 10. The system of claim 1 wherein said bioadhesive is a mucoadhesive.
 11. The system of claim 1 wherein said system remains active for a period between about ten minutes and about 3 months.
 12. The system of claim 1 wherein said nano-particles adhere to said oral cavity or mucous membranes of various tissues.
 13. The system of claim 1 wherein said nano-particles provide one or more of the following site specific adhesion: settling around the gumline; settling subgingivally; penetrating into periodontal pocket; adhering to soft tissue; and becoming immobilized over an extended period of time.
 14. A controlled release delivery system for delivery to biological surfaces comprising an oral cavity or mucous membranes of various tissues, said system comprising: a plurality of solid nano-particles, each of said solid nano-particles comprising a core formed of a hydrophobic material selected from the group consisting of natural waxes, synthetic waxes, fatty acid esters, fatty alcohols, solid hydrogenated plant oils, biodegradable natural polymers and synthetic polymers, and an effective amount of a first active agent contained therein and bioadhesive positively charged surfactant entrapped on a surface of each of said solid nano-particles surrounding said core, wherein said positively charged surfactant is selected from the group consisting of straight-chain alkylammonium compounds, cyclic alkylammonium compounds, petroleum derived cationics, and polymeric cationic materials, and wherein said nano-particles have an average particle diameter between about 0.01 microns and about 10 microns.
 15. The system of claim 1 wherein said nano-particles further comprise a preservative.
 16. The system of claim 1 wherein said positively charged surfactant includes hydrophobic and hydrophillic ends said hydrophobic ends of said positively charged surfactant are embedded in said core and said hydrophilic ends of said positively charged surfactant are exposed on a surface of said core.
 17. The system of claim 1 wherein said nano-particles further comprise a co-surfactant selected from the group consisting of phospholipids, cholates, polysorbates, polyethyleneglycol esters, polyethoxylated fatty acids, poly(oxyethylene)poly(oxypropylene) block copolymers, polyoxyethylene fatty alcohol ethers, polyoxyethylene nonylphenyl ethers, and polyoxyethylene isooctylphenyl ethers.
 18. The system of claim 1 wherein said nano-particles are present in an aqueous continuous phase suspending a colloidal phase of said nano-particles.
 19. A method for producing a system for delivery to biological surfaces comprising an oral cavity or mucous membranes of various tissues, said system comprising: a plurality of solid nano-particles, each of said solid nano-particles comprising a core and an effective amount of a first active agent contained therein and a bioadhesive positively charged surfactant entrapped on a surface of each of said solid nano-particles surrounding said core, said method comprising the steps of: (i) heating a core material forming said core to a temperature above said core material melting point to form a melt; (ii) dispersing said first active agent into said melt; (iii) dispersing said positively charged surfactant in the aqueous phase; (iv) heating the dispersion to a suspension above the melting point of the mixture formed in step (ii) to form a hot melt; (v) mixing said hot melt of step (ii) with the aqueous solution formed in step (iii) to form a suspension; (vi) high shear homogenization of said suspension at a temperature above the melting temperature of said material mixture formed in step (v) until a homogeneous fine suspension is obtained; and (vii) rapidly cooling said suspension to below the melting point of the core material mixture formed in step (v).
 20. An oral hygiene product comprising the system of claim
 1. 